CVE-2026-44427: Github.com/modelcontextprotocol/registry MCP Registry Has Open Redirect Vulnerability
MODERATECVE-2026-44427 is a MODERATE mcp registry has open redirect vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Github.com/modelcontextprotocol/registry libraries in the Go ecosystem. The issue involves mcp registry has open redirect via protocol-relative path in trailing-slash middleware. Remediation is available by upgrading affected packages to version 1.7.5.
CVE-2026-44427 at a Glance
How to Fix CVE-2026-44427
To remediate this vulnerability, upgrade all affected Github.com/modelcontextprotocol/registry dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/modelcontextprotocol/registry to 1.7.5Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/modelcontextprotocol/registryHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-44427, inspect your project dependencies for Github.com/modelcontextprotocol/registry:
inspect dependencies for github.com/modelcontextprotocol/registryAnalyze the terminal output to locate any version of Github.com/modelcontextprotocol/registry in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.7.5), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Github.com/modelcontextprotocol/registry, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-44427 Affected Github.com/modelcontextprotocol/registry Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/modelcontextprotocol/registry
|
Go |
≥ 1.1.0
< 1.7.5
|
1.7.5
|
References
Frequently Asked Questions
What is CVE-2026-44427?
Which Github.com/modelcontextprotocol/registry versions are affected?
What version fixes CVE-2026-44427?
Is github.com/modelcontextprotocol/registry affected?
What CWE is associated with CVE-2026-44427?
How can I check Go dependencies for CVE-2026-44427?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-v8vw-gw5j-w7m6",
"modified" : "2026-05-15T23:47:07Z",
"published" : "2026-05-08T17:02:12Z",
"aliases" : [ "CVE-2026-44427" ],
"summary" : "MCP Registry has open redirect via protocol-relative path in trailing-slash middleware",
"details" : "### Summary\nThe TrailingSlashMiddleware in internal/api/server.go is vulnerable to an open redirect attack. An attacker can craft a URL with a protocol-relative path (e.g., //evil.com/) that, after trailing slash removal, results in a Location header of //evil.com — which browsers interpret as an absolute URL to an external domain.\n\n### Details\nThe TrailingSlashMiddleware strips trailing slashes from request paths and issues a 308 Permanent Redirect to the cleaned path. However, it does not validate or sanitize the resulting path before using it as the redirect target.\n\nWhen a request is made with a path like //evil.com/, the middleware processes it as follows:\n\n### PoC\n1. Start the registry server locally or identify a deployed instance\n2. Send a request with a double-slash path followed by an external domain:\n`curl -v https://<registry-host>//evil.com/`\n<img width=\"3066\" height=\"969\" alt=\"image\" src=\"https://github.com/user-attachments/assets/a5305f00-29bf-4708-952a-478d608f2074\" />\n3. Observe the 308 Permanent Redirect response with Location: //evil.com:\n4. When accessed in a browser, the user is redirected to https://evil.com\n\n\n\n### Impact\n**Phishing**: Attackers can abuse the trusted registry domain to redirect users to credential-harvesting pages\n**Malware distribution**: Redirect users to sites serving malicious downloads\n**Trust abuse:** Links originating from the official MCP Registry domain carry implicit trust",
"severity" : [ {
"type" : "CVSS_V4",
"score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/modelcontextprotocol/registry"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.1.0"
}, {
"fixed" : "1.7.5"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-v8vw-gw5j-w7m6"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44427"
}, {
"type" : "WEB",
"url" : "https://github.com/modelcontextprotocol/registry/pull/1227"
}, {
"type" : "WEB",
"url" : "https://github.com/modelcontextprotocol/registry/commit/1201cbd82b2cf6d4b56edfc05c763059a12f9fdb"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/modelcontextprotocol/registry"
}, {
"type" : "WEB",
"url" : "https://github.com/modelcontextprotocol/registry/releases/tag/v1.7.5"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-601" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-05-08T17:02:12Z",
"nvd_published_at" : "2026-05-14T22:16:44Z"
}
}